Counterirritants

Counterirritants are substances or treatments that produce a mild, localized irritation in one area of the body with the aim of alleviating pain in another area. They are commonly used in topical analgesic products for musculoskeletal pain, sprains, strains, and arthritis. The proposed mechanism involves stimulating cutaneous nerves to generate a competing sensation such as cooling, warming, tingling, or redness, which can help modulate nociceptive input in the affected region. Some agents may also enhance local blood flow or cause temporary desensitization of peripheral nerves, contributing to pain relief.

Typical counterirritants include menthol (cooling sensation), camphor, methyl salicylate (oil of wintergreen), and eucalyptus oil. Capsaicin is sometimes listed as a counterirritant because of its initial irritant effect and subsequent analgesia through nociceptor desensitization, though its primary action is often described as a desensitizing topical agent.

They appear in rubs, creams, gels, ointments, liniments, and medicated plasters or patches. They are intended for short-term relief of minor aches and are not substitutes for medical evaluation of deeper or persistent pain. Care should be taken to avoid broken skin, eyes, or mucous membranes; skin irritation or dermatitis can occur in sensitive individuals. Ingestion or excessive application can pose health risks, particularly with methyl salicylate in children.

Evidence supports modest short-term relief for some conditions, but results are variable and they are generally considered adjunctive therapies rather than curative treatments.